;;; -*-scheme-*-

;;; Mes --- Maxwell Equations of Software
;;; Copyright © 2016 Jan Nieuwenhuizen <janneke@gnu.org>
;;;
;;; base.mes: This file is part of Mes.
;;;
;;; Mes is free software; you can redistribute it and/or modify it
;;; under the terms of the GNU General Public License as published by
;;; the Free Software Foundation; either version 3 of the License, or (at
;;; your option) any later version.
;;;
;;; Mes is distributed in the hope that it will be useful, but
;;; WITHOUT ANY WARRANTY; without even the implied warranty of
;;; MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
;;; GNU General Public License for more details.
;;;
;;; You should have received a copy of the GNU General Public License
;;; along with Mes.  If not, see <http://www.gnu.org/licenses/>.

(define (cons* x . rest)
  (define (loop rest)
    (if (null? (cdr rest)) (car rest)
        (cons (car rest) (loop (cdr rest)))))
  (loop (cons x rest)))

(define-macro cond
  (lambda clauses
    (if (null? clauses) *unspecified*
        (if (null? (cdr clauses))
            (list 'if (car (car clauses))
                  (cons* 'begin (car (car clauses)) (cdr (car clauses)))
                  *unspecified*)
            (if (eq? (car (cadr clauses)) 'else)
                (list 'if (car (car clauses))
                      (cons* 'begin (car (car clauses)) (cdr (car clauses)))
                      (cons* 'begin *unspecified* (cdr (cadr clauses))))
                (list 'if (car (car clauses))
                      (cons* 'begin (car (car clauses)) (cdr (car clauses)))
                      (cons* 'cond (cdr clauses))))))))